Semi-Active Laser (SAL) guided missile systems are used when destruction of a specific target requires precision. In some cases, such precision is needed to minimize collateral damage. In some cases, such precision is desired to ensure that a high-value target is successfully destroyed.
The principle of operation of SAL guided missile systems is to “paint” or designate a target with a signal that is perceivable by a missile. A system called a seeker is responsible for perceiving the signal reflected by the designated target. A forward-positioned operator may paint the desired target using a Laser Target Designator (LTD), for example. An LTD can have a Short-Wave Infrared Radiation (SWIR) laser to illuminate or paint the target. In some embodiments, the illumination signal is encoded with an identifying signal corresponding to the specific LTD providing the illumination. The illumination signal can be detected, however, by persons or systems nearby, thereby exposing the forward-positioned operator.
The seeker of the SAL guided missile can be equipped with a SWIR detector, which can be configured to detect SWIR signals and to determine whether the detected SWIR signals are encoded with the identifying signal corresponding to the LTD to which the guided missile is paired. If the SWIR detector determines that the detected SWIR signals are encoded with the signature of the paired LTD, then the target from which the detected signal is reflected is deemed to have been designated by the paired LTD. The seeker then can sense this reflected designation signal and also can determine the direction of the designated target relative to the guided missile. The seeker may output a signal indicative of the determined direction for use by a guidance system on the missile. The missile's guidance system then can direct the missile to the designated target.
Some seekers also can have a passive Image InfraRed (IIR) target location system. Such seekers are sometimes called dual-mode seekers. The passive IIR target locator can include an infrared camera to capture images of a scene that includes the target designated by the LTD. Image features corresponding to the designated target can be identified. Image coordinates of the identified features within the captured images can be used to determine the direction of the target relative to the missile. The signal strength of the ambient infrared light emitted from and/or reflected by the imaged scene can be much lower than the signal strength of the pulsed laser signal generated by an LTD and reflected by the target. Thus, target detection and location using an IIR-mode of operation can be performed when the range between the target and missile is relatively close. For long-range target detection and location, SAL-mode operation can be better used, due to the relatively high signal strength of the LTD laser signal.
A dual-mode guided missile can be launched by a launching vehicle that is located a great distance from a desired target. The dual-mode seeker of such a launched missile might first acquire a target using the SAL-mode of target detection and location, due to the relatively large signal strength of the LTD laser signal. When the range to the designated target closes to a distance at which the passive IIR-mode of target detection and location can be used, the seeker can switch modes to the IIR-mode of operation.
Often more than one guided missile may be deployed at the same time. Coordinating the targeting of multiple targets and multiple guided missiles can be problematic. Coordinating multiple targets can involve multiple forward-positioned operators, each of whom incurs a risk of being detected. In some cases, two or more passively guided missiles may redundantly select the same target, unnecessarily wasting military assets.